Defining Stream Fish Microhabitat Requirements for Water Project Planning

Brown trout daily activities were divided into two braod categories, resting and feeding, and the population was divided into three size groups (one of which is reported on here), based on the timing and location of these activities. Microhabitat components, measured previously in four rivers at sites occupied by fish, were utilized to develop usable componenet ranges for each size group and activity to illustrate the breadth of component values utilized out of the total range available. Microhabitat is thus described as a range of numerical values for each componenet of a specific set of components. A 90 meter section of the Blacksmith Fork River in northern Utah was mapped by measuring depth, current velocity and light. A scuba diver searched the area, locating and identifying brown trout according to size group and activity. A comparison of fish locations with the mpas indicates the maps correctly identified a high percentage of the sites occupied by brown trout. A chi-square test of the probability of uniform distribution of fish was significant for both feeding and resting sites. Microhabitat components which most effectively regulate brown trout distribution in this type of intermountain strean can thus be described and measured, and used to estimate the porportion of a stream which is habitable. These quantified components should enable the designing of stream channel alterations to provide proper trout microhabitat